Amplifier Damage

@carlsbad it's close.. In my setup, what happened was, I had the unit that was in stand by connected and being fed with the audio signal. However, the internal relay switch of the Standby unit is automatically disengaged to not let the signal go through.. Yes!! it's very similar to your setup..  

I recently rewired my tube amp and now have two inputs, one balanced with a transformer input, and one RCA.  I put in a selector switch.  

Currently I have both RCA and XLR hooked up to my preamp so I can select and listen to one and then the other for AB testing.  I think this is similar to what you are reporting with your luxman, When one input is selected, the other one is disconnected.  Non problem.

Jerry

Okay guys, I was just on the phone with Luxman service.. It's all good, every Luxman component has relays in the Input and Output stages. That's the clicking sound that you hear when you select and deselect input and output options. So when the 550AXII is in stand by mode, the input relays are disconnected. So what ever signal I presented at the input is not passed through. And the D03X is designed to be active for both Unbalanced and balanced output at the same time. They suggested I could experiment turning on and off one of the equipment to see if it makes any difference in the sound of the one still connected. Although, they said it is safe to try that.. I am not venturing that route.. When I get the C900U in a couple of weeks, I'll have these separate setups.. Hope that helps..

An amplifier's input stage can be overloaded by a bad upstream component which has too much voltage. 

A preamp with too many outputs connected may no longer perform correctly as the impedance becomes too low.  It is rare that shorting a preamp (impedance = 0) would cause damage but theoretically possible depending on design.  Usually the output impedance of a preamp is high enough that it is self protecting.

Can anyone further clarify on this issue? 

This sounds like something I have done in the past. If I am breaking in a new component, say a preamp for example, I wouldn't turn the amplifier on when not listening. I would just let the preamplifier continue to play.  

Similarly my Pass preamp is on all the time while my Pass amplifier is on standby. Is this a potential scenario where the amplifier can become damaged? 

How would one run something out of the tape output? Say for example a headphone amp. You couldn't listen to one over the other without disconnecting? 

All good @rman9 

I inadvertently hooked up a second preamp output to another devices RCA output.
Our courser the speaker went pretty quiet as one source was driving 0v and the other signal, so you get a voltage divider.

But they are made to do that, or the poutoput impedance would be s closer to 0-ohms, that t50, 500, or #k ohms.

(Probably also why people with high output impedance have more cable effect than ones using a lower output impedance preamp.)

I would not fret, but it is better to ask Luxman as they know their stuff more intimately.

I’ll look forwards to seeing what they tell you.

@holmz the integrated that I had swtiched off(Standby), but connected to the unbalanced out of the Active Luxman D03X DAC is the Luxman 550AXII. The balanced out was connected to the Luxman 595ASE which I was listening to. So I dived into the block diagram of the 550AXII, looks like the input signal goes through several gating switches for Tone control, Subsonic control, goes through a buffer before it hits the multi step ladder circuitry of the volume control. All this is in the path before it sees the Preamp circuit. So I am not sure, how far the audio signal goes through when the Unit is in stand by mode. I might call Luxman tomorrow to get more insight into this.. 

fine, but I had the nagging question. Does the input audio signal get shunted to ground through a diode in the input amp stages when its powered off or something to protect the circuitry? 

Any inputs will be great

With a DMM one could measure the input impedance with the amp on and off.
I have never heard of an amp shunting the input to ground.
Even if it did the output impedance of the DAC or preamp would mean that the DAC would not suffer,

Subjectively one would hear the level drop if the amp that was powered off was shunted to ground. And we never hear that.

@russ69 Thank you!! it was accidental.. I am usually careful with things like this.. But it was a miss yesterday.. Hopefully it's not a permanent damage.. 

Sorry but you should not do that, it should be fully disconnected, not just off. The preamp is seeing the idle amp as a load. Sometimes OK sometimes not.

@cd318 loved reading your response.. The last four sentences are the best and typically I try to lead my life 😊 that way.. too much seriousness would lead to health issues anyways.. 

Coincidentally, both Amps are Class A.. But again, no damage done.. So I'll move on and enjoy the music.. Thanks again..  

@rman9

Amps are weird in that things can go wrong even whilst they’re not doing much.

All it would take is for just one component to fail...

It’s extremely rare, but not impossible.

However, in your case I don’t think there’s anything to worry about as the all important heat generating circuits were switched off. And even if they weren't, so what?

The general consensus seems to be that’s it better to leave your amp on rather than to keep powering it on and off.

Unless you’re talking heat generating Class A designs - or tubes.

With those you’d probably be better off powering them up for the listening duration only.

In any case, it’s just one of those things not worth worrying about when you want to immerse yourself in the music.

A bit like a meteorite hitting your house or Yellowstone Park erupting at an inopportune moment.

If it happens, it happens.

No point in worrying about such infinitely remote possibilities when your seeking pure sonic pleasure.